Nickel-base alloy

ABSTRACT

A cast nickel-base alloy containing about 5.75 percent aluminum, about 0.015 percent boron, about 0.11 percent carbon, about 10 percent cobalt, about 8 percent chromium, about 1.5 percent hafnium, about 2 percent molybdenum, about 4 percent tantalum, about 1 percent titanium, about 8 percent tungsten and about 0.08 percent zirconium.

United States Patent 11 1 1111 3,753,698 Lund 1 Aug. 21, 1973 [54] NICKEL-BASE ALLOY 3,615,377 10 1971 Quigg et al. 75/171 [75] Inventor: Carl H. Lund, Arlington Heights, [11.

Primary Examiner-Richard 0. Dean [73] Asslgnee' m Metals Company Wheelmg Attorney-John A. Crowley, Jr. and Francis J. Mulligan, Jr. [22] Filed: Jan. 22, 1971 [21] Appl. No.: 108,846 [57] ABSTRACT A cast nickel-base alloy containing about 5.75 percent 2 l. E2 g li alummum, about 0.015 percent boron, about 0.1 1 per- [58] Fie'ld 148/32 cent carbon, about 10 percent cobalt, about 8 percent 148/32 chromium, about 1.5 percent hafnium, about 2 percent molybdenum, about 4 percent tantalum, about 1 per- 56] References cited cent titanium, about 8 percent tungsten and'about 0.08

t I UNITEDSTATES PATENTS percen z'rcomum 3,526,499 9/1970 Quigg et a1. 75/171 3 Claims, 2 Drawing Figures lOOOX PATENTED mm I975 IOOOX CARL H LUND INVENTOR NICKEL-BASE ALLOY In U.S. applications Ser. Nos. 725,074, filed Apr. 29, 1968, now abandoned and 841,505, filed July 14, 1969, now abandoned it was disclosed that addition of hafnium to certain nickel-base cast alloys resulted in various improvements in characteristics thereof. One of the alloys disclosed in that application as being improved by the addition of hafnium was identified as Alloy B. As modified with hafnium, Alloy B contained (in percent by weight) about 6 percent aluminum, about 0.01 5 percent boron, about 0.10 percent carbon, about percent cobalt, about 8 percent chromium, about 1.5 percent hafnium, about 6 percent molybdenum, about 4.25 percent tantalum, about 1 percent titanium, about 0.075 percent zirconium with the balance being essentially nickel. Naturally, this alloy can vary in composition somewhat within a closely controlled commercial specification. As disclosed in application Ser. No. 841,505, filed July 14, 1969, now abandoned the hafnium can vary from about 1 percent to about 3 percent with the preferred amount being about 1.5 percent.

It has now been discovered that a modification of this hafnium-containing alloy wherein a major portion of the contained molybdenum is replaced by an atomic equivalent of tungsten exhibits greatly enhanced characteristics of engineering significance.

It is an object of the invention to provide a novel, highly advantageous alloy.

Another object of the invention is to provide castings made of the novel alloy of the invention having highly advantageous characteristics.

Other objects and advantages will become apparent from the following specification taken in conjunction with thedrawing which illustrates the microstructure of the novel cast alloy of the present invention.

Generally speaking, the present invention comprises a cast alloy consisting, in percent by weight, of about 5.5 percent to about 6.25 percent aluminum, about 0.002 percent to about 0.05 percent boron, about the 0.07 percent to about 0.16 percent carbon, about 8 percent to about 12 percent cobalt, about 7 percent to about 9.5 percent chromium, about 0.8 percent to about 3.5 percent hafnium, about 1.5 percent to about 2.5 percent molybdenum, about 3.75 percent to about 5 percent tantalum, about 0.75 percent to about 1.5 percent titanium, about 7 percent to about 9 percent tungsten, about 0.01 percent to about 0.20 percent zirconium with the balance, except for impurities and incidental elements, being nickel. The composition of the alloy of the present invention should be balanced so as to obtain optimum cast alloy characteristics by maintaining the total of the percents of aluminum plus titanium at about 6.4 percent to about 7.2 percent and by maintaining the sum of the molybdenum percentage plus one-half the tungsten percentage at about 6 percent. As those skilled in the art will appreciate, the alloy of the present invention should be made of the purest materials commercially practical and should be melted and cast under vacuum.

An illustrative alloy of the present invention contains in percent by weight about 5.75 percent aluminum, about 0.015 percent boron, about 0.1 1 percent carbon, about 9.8 percent cobalt, about 7.75 percent chromium, about 1.4 percent hafnium, about 2 percent molybdenum, about 4.2 percent tantalum, about 0.9 percent titanium, about 8 percent tungsten, about 0.08

Tensile Test (77F.) (25C.)

138.4 ksi (97.4 Kg/mm) ll4.0 ksi (80.2 Kg/mm) 8 6% Ultimate tensile strength 0.2% yield strength Elongation Reduction in area Creep-Rupture l4001'F. (760C.)

Load-94 ksi (66.1 Kg/mm') -97 ksi (68.2 Kg/mm) Life-to-Rupture 366.6 hours 276.2 hours Elongation 3.4% 5.5% Prior Creep 3.52% 4.84% Reduction in Area 10.3% 6.9%

Creep-Rupture 18001F. (982C.)

Load-29 ksi 20.9 Kg/mm Life-to-Rupture 75.1 hours Elongation 7.8% Reduction in Area 6.9%

The data set forth in the foregoing; table shows that the alloy of the present invention exhibits, in specimens machined from cast turbine hardware, a life-to-rupture at l,400 F. which is about four times the life-torupture of modified Alloy B. At l,800 F. the life-torupture of the alloy of the present invention is substantially higher than the life-to-rupture of modified Alloy B The microstructure of the alloy of the present invention is depicted in the attached drawing under 250 X and 1000 X. The photo-micrographs were taken of alloy samples etched with an etchant made up by mixing 30 ml. of glycerol, 8 ml. of concentrated nitric acid and 6 ml. of 48 percent hydrofluoric acid.

The alloy of the present invention is particularly adapted to be used in the vacuum-cast condition as parts and structures subjected in use to high tensile forces at various temperatures extending over a temperature range of 1,000 to 1,800 F. and even higher. In particular, the alloy of the present invention is useful as parts and structures for gas turbines, said parts and structures being fabricated by investment casting technique.

While the present invention has been described in conjunction with advantageous embodiments, those skilled in the art will recognize that modifications and variations may be resorted to without departing from the spirit and scope of the invention. Such modifications and variations are considered to be within the purview and scope of the invention.

I claim:

1. A cast, nickel-base alloy consisting in percent by weight of about 5.5 percent to about 6.25 percent aluminum, about 0.002 percent to about 0.05 percent boron, about 0.07 percent to about 0.16 percent carbon, about 8 percent to about 12 percent cobalt, about 7 percent to about 9.5 percent chromium, about 0.8 percent to about 3.5 percent hafnium, about 1.5 percent to about 2.5 percent molybdenum, about 3.75 percent to about 5 percent tantalum, about 0.75 percent to cent aluminum, about 0.015 percent boron, about 0.1 1 percent carbon, about 9.8 percent cobalt, about 7.75 percent chromium, about 1.4 percent hafnium, about 2 percent molybdenum, about 4.2 percent tantalum, about 0.9 percent titanium, about 8 percent tungsten, and about 0.08 percent zirconium.

3. An alloy of claim 1 in the form of a vacuum-cast turbine blade. 

2. An alloy as in claim 1 containing about 5.75 percent aluminum, about 0.015 percent boron, about 0.11 percent carbon, about 9.8 percent cobalt, about 7.75 percent chromium, about 1.4 percent hafnium, about 2 percent molybdenum, about 4.2 percent tantalum, about 0.9 percent titanium, about 8 percent tungsten, and about 0.08 percent zirconium.
 3. An alloy of claim 1 in the form of a vacuum-cast turbine blade. 